The backlight module is provider of light source for the liquid crystal display (LCD). All the colors showed by the liquid crystal display are derived from the light emitted by the backlight module. Currently commercially available light sources in the backlight module are mainly divided into two types, i.e., cold cathode fluorescent lamp (CCFL) and light emitting diode (LED). Compared the two light sources, LEDs have obvious advantages in the aspects of energy saving, environmental protection, small size, long life, and so on. As the cold cathode fluorescent lamp contains mercury, it not only results in high cost but also harms the environment greatly. To protect the environment, gradually replacing cold cathode fluorescent lamp with LEF will be an inevitable result. But, for the color saturation showed by the liquid crystal display, the light emitted from the cold cathode fluorescent lamp has good color saturation, and the color saturation of ordinary white LEDs is relatively poor. Therefore, it is very important to improve the color saturation of the liquid crystal display with LED light source.
The color saturation of LCD is usually shown with the NTSC color gamut which is the sum of color shown by the display under the NTSC standard. The color gamut of ordinary white light LED is 68-70% NTSC, it is very negative for the color performance of display. Currently there are two main ways to improve the color gamut of LED. The first method requires use of many LED light sources which are able to emit different colors to make color saturation exceeding 90% NTSC color gamut. Due to the higher costs of the LED light sources with different colors, the working life of the LED light sources are uneven. As a result, this method cannot be universally used. The second method requires use of ordinary white LED which emits mainly blue light. By using quantum dots, a portion of the blue light is converted into red light and green light. Compared with the white light emitted by the traditional LED, more red, green, and blue light goes through the filter and therefore displaying brighter, richer colors. But as the cost of quantum dot is higher, this method requires consideration of the light conversion efficiency of the quantum dots, stability, and other factors.